U.S. patent number 4,983,653 [Application Number 07/333,977] was granted by the patent office on 1991-01-08 for polyester shrinkable film containing benzotriazole.
This patent grant is currently assigned to Diafoil Company, Ltd.. Invention is credited to Yujiro Fukuda, Hiromi Yamashita.
United States Patent |
4,983,653 |
Fukuda , et al. |
* January 8, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Polyester shrinkable film containing benzotriazole
Abstract
Disclosed herein is a polyester shrinkable film. The film
according to the present invention can provide extremely excellent
durability and long-time storability of contents of a container in
labelling and shrink packaging use.
Inventors: |
Fukuda; Yujiro (Machida,
JP), Yamashita; Hiromi (Yokohama, JP) |
Assignee: |
Diafoil Company, Ltd. (Tokyo,
JP)
|
[*] Notice: |
The portion of the term of this patent
subsequent to May 2, 2008 has been disclaimed. |
Family
ID: |
27572156 |
Appl.
No.: |
07/333,977 |
Filed: |
April 6, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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119623 |
Nov 12, 1987 |
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Foreign Application Priority Data
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Nov 12, 1986 [JP] |
|
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61-269251 |
Dec 11, 1986 [JP] |
|
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61-295590 |
Dec 15, 1986 [JP] |
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61-298427 |
Feb 17, 1987 [JP] |
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62-33731 |
Mar 11, 1987 [JP] |
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62-56236 |
Jun 11, 1987 [JP] |
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62-145753 |
Oct 26, 1987 [JP] |
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62-269765 |
Apr 9, 1988 [JP] |
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63-87948 |
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Current U.S.
Class: |
524/91; 528/305;
528/308.1; 528/308.2 |
Current CPC
Class: |
B29C
61/003 (20130101); C08J 3/226 (20130101); C08K
5/3475 (20130101); C08K 5/3475 (20130101); C08L
67/02 (20130101); B29C 35/049 (20130101); B29K
2067/00 (20130101); C08J 2367/02 (20130101); C08J
2467/00 (20130101) |
Current International
Class: |
B29C
61/00 (20060101); C08J 3/22 (20060101); C08J
3/20 (20060101); C08K 5/00 (20060101); C08K
5/3475 (20060101); B29C 35/04 (20060101); C08K
005/34 (); C08G 063/00 (); C08G 063/88 () |
Field of
Search: |
;528/308.2,308.1,305,502
;524/91 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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210646 |
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Feb 1987 |
|
EP |
|
1187792 |
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Feb 1965 |
|
DE |
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57-42726 |
|
Mar 1982 |
|
JP |
|
57-119941 |
|
Jul 1982 |
|
JP |
|
57-119941 |
|
Jul 1982 |
|
JP |
|
57-159618 |
|
Oct 1982 |
|
JP |
|
57-194950 |
|
Nov 1982 |
|
JP |
|
59-45202 |
|
Mar 1984 |
|
JP |
|
59-97175 |
|
Jun 1984 |
|
JP |
|
60-206839 |
|
Oct 1985 |
|
JP |
|
60-232948 |
|
Nov 1985 |
|
JP |
|
60-253545 |
|
Dec 1985 |
|
JP |
|
61-64430 |
|
Apr 1986 |
|
JP |
|
60-64430 |
|
Apr 1986 |
|
JP |
|
61-203161 |
|
Sep 1986 |
|
JP |
|
62-95341 |
|
May 1987 |
|
JP |
|
63-55052 |
|
Mar 1988 |
|
JP |
|
825549 |
|
Dec 1959 |
|
GB |
|
989080 |
|
Apr 1965 |
|
GB |
|
Primary Examiner: Kight, III; John
Assistant Examiner: Daley; Dennis R.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation-in-part application of U.S. Patent
application Ser. No. 119,623 filed Nov. 12, 1987 which is still
pending.
Claims
What is claimed is:
1. A polyester shrinkable film containing from 0.1 to 20% by weight
of an ultraviolet absorber having 10% weight loss temperature
(T.sub.10) upon thermogravimetric analysis of not lower than
200.degree.C., which film has a shrinkage from 30 to 80% in one
direction of either the longitudinal direction or the transverse
direction and a shrinkage from -5 to 10% in the other direction
perpendicular to the main shrinking direction after treatment of 5
minutes at 100.degree. C. in an air oven, and a light transmittance
at a wavelength of 390 nm of not greater than 20%.
2. The polyester shrinkable film according to claim 1, wherein the
ultraviolet absorber is selected from the group consisting of
benzophenone type absorbers, benzotriazole type absorbers,
salicylic acid derivative type absorbers, cyanoacrylate type
absorbers and oxalic acid anilide type absorbers.
3. The polyester shrinkable film according to claim 1, wherein the
ultraviolet absorber is
2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole.
4. The polyester shrinkable film according to claim 1, wherein the
ultraviolet absorber is
2-(2'-hydroxy-5'-methylphenyl)benzotriazole.
5. The polyester shrinkable film according to claim 1, wherein the
ultraviolet absorber is 2-[2'-hydroxy-3',5'-bis (.alpha.,.alpha.-
dimethylbenzyl)phenyl]-2H-benzotriazole.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a shrinkable film excellent in
durability upon transportation of containers, long-time storability
of contents in the containers, etc.
In recent years, shrinkable films have generally been used for
labeling for containers such as PET bottles, glass bottles, etc. or
shrink packaging applications. However, shrinkable films in the
prior art involve problems in view of the durability and the
long-time storability when they are used for labeling or shrink
packaging application. That is, in containers labeled or applied
with close packaging by means of shrinkable films such as of
polyvinyl chloride or polystyrene, the films have often been broken
due to the contact of the containers with each other upon
long-distance transportation of the containers to bring about a
problem in view of the appearance.
On the other hand, in the case of applying shrink packaging to
those containers filled with brewages such as Japanese sake, beer
or wine, since both of the container and the shrinkable film are
highly transparent, when the containers are exposed to direct
sunlight they inevitably suffer from degradation in the quality of
the filled drinks, particularly, due to ultraviolet rays.
With the reason as described above, there has been strongly
demanded for a shrinkable film excellent in the durability upon
transportation of containers and also excellent in long-time
storability of the content.
In view of the foregoing problems, the present inventors have made
an earnest study and have accomplished the present invention based
on the finding that the durability and the long-time storability
can be improved by using a polyester shrinkable film having
specified shrinking characteristic and ultraviolet ray-absorbing
characteristic.
SUMMARY OF THE INVENTION
In an aspect of the present invention, there is provided a
polyester shrinkable film containing from 0.1 to 20% by weight of a
ultraviolet ray absorber having a shrinkage of not less than 20% in
one of longitudinal and transverse directions and not greater than
15% in the other direction of a film after treatment for five
minutes at 100.degree. C. in air oven, and light transmittance of
the film at a wave length of 390 nm of not greater than 20%.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a polyester shrinkable film having
a shrinkage of not less than 20% in one of longitudinal or
transverse directions and not greater than 15% in the other
direction of the film after the treatment for five minutes at
120.degree. C. in air oven, and light transmittance of the film at
a wave length of 30 nm not greater than 20%.
The polyester used in the present invention may be any of
homopolyesters or copolyesters comprising, as the carboxylic acid
component, one or more of known dicarboxylic acids such as
terephthalic acid, oxalic acid, malonic acid, succinic acid, adipic
acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid,
naphthalene dicarboxylic acid and diphenylether dicarboxylic acid
and, as the diol component, one or more of known diol such as
ethylene glycol, neopentyl glycol, propylene glycol, trimethylene
glycol, tetramethylene glycol, hexamethylene glycol, diethylene
glycol, polyalkylene glycol and 1,4-cyclohexane dimethanol.
As the copolyester, those obtained by using two or more of
dicarboxylic acids and/or diols as the dicarboxylic acid component
and/or diol component. Also, polyester prepared by using other
ingredients, for example, hydroxycarboxylic acid such as
p-hydroxybenzoic acid and p-hydroxyethoxybenzoic acid,
mono-functional compound such as benzoic acid, benzoyl benzoic
acid, methoxypolyalkylene glycol, polyfunctional compound such as
glycerin, penthaerythritol, trimethyrol and trimethylene propane
within such a range that the product can be substantially a linear
high molecular can also be used.
As the polyester usable in the present invention, those
copolyesters in which the dicarboxylic acid component mainly
comprises terephthalic acid, the diol component mainly comprises
ethylene glycol, and the copolymer ingredient comprises isophthalic
acid and phthalic acid as the dicarboxylic acid component and
neopentyl glycol, diethylene glycol, polyalkylene glycol and, if
required, 1,4-cyclohexane dimethanol as the diol component are
preferred since they are available industrially at a reduced cost
and show satisfactory shrinking property for the resultant
film.
In the polyester used in the present invention, not less than 70
mol %, more preferably, not less than 75 mol % of the dicarboxylic
acid component is a terephthalic acid unit, while not less than 70
mol %, more preferably, not less than 75 mol % of the diol
component is an ethylene glycol unit. Those copolyesters with the
terephthalic acid unit and/or ethylene glycol unit is less than 70
mol % are not preferred since the strength and the solvent
resistance of the resultant film are poor.
Further, those polymers other than the polyester may be admixed to
the polyester described above so long as the amount added is not
greater than 30 mol % based on the entire amount of the
mixture.
Further, fine particles of organic and inorganic lubricants, etc.
may preferably be incorporated in order to improve the slipperiness
of the film. Further, additives such as stabilizer, colorant,
antioxidant, defoamer, antistatic agent, etc. may also be
incorporated as required. As fine particles for providing a good
slipperiness, there can be mentioned those known inert external
particles such as kaolin, clay, calcium carbonate, silicon oxide,
potassium terephthalate, aluminum oxide, titanium oxide, calcium
phosphate, lithium fluoride and carbon black and; high melting
organic compounds not melted upon molten film formation of
polyester resin; crosslinked polymer and internal particles formed
at the inside of polyesters upon production thereof by metal
catalyst, for example, alkali metal compound, alkaline earth metal
compound, etc. used for the synthesis of the polyester. The fine
particles contained in the shrinkable film is preferably from 0.005
to 5.0% by weight and the preferred average particle size is from
0.001 to 3.5 .mu.m.
The light transmittance of the shrinkable film according to the
present invention at a wave length of 390 nm is from 0.1 to 20%,
preferably from 0.1 to 10% and, more preferably from 0.1 to 5%.
Those films having light transmittance over 20% are insufficient
for the absorption capacity for the entire ultraviolet region and
can not provide long-time storability for the contents of
containers. In a case where they are applied to containers of
brewages such as sake and wine, the contents are remarkably
discolored due to oxidation.
For providing the film with ultraviolet absorbing capacity, it is
possible to dispose a coating layer on the film surface during or
after the production of the film, ultraviolet absorbers are usually
contained in the polyester. The ultraviolet absorber can be
selected, for example, from benzophenones, benzotriazoles,
salicylic acid derivatives, cyanoacrylates, oxalic acid anilide,
etc. and, particularly, those ultraviolet absorbers having 10%
weight loss temperature (T.sub.10) upon thermogravimetric analysis
of not lower than 200.degree. C., preferably, not lower than
220.degree. C. are preferred since the contaminations in each of
the production steps can be reduced. If T.sub.10 is lower than
200.degree. C., sublimation or decomposition is undesirably caused
to the ultraviolet absorbers.
As the benzophenone type ultraviolet absorber, there can be
mentioned, for example,
2-hydroxybenzophenone,
2,4-dihydroxybenzophenone,
2-hydroxy-4-methoxybenzophenone,
2-hydroxy-4-octoxybenzophenone,
2-hydroxy-4-dodecyloxybenzophenone,
2-hydroxy-4-octadecyloxybenzophenone,
2-hydroxy-4-(2-hydroxy-3-methacryloxy)-propoxybenzophenone,
2-hydroxy-4-chlorobenzophenone,
2-hydroxy-4-methoxy-5-sulfobenzophenone,
2-hydroxy-4-methoxy-2'-carboxybenzophenone,
2,2'-dihydroxybenzophenone,
2,2'-dihydroxy-4-methoxybenzophenone,
2,2'-dihydroxy-4,4'-dimethoxybenzophenone,
2,2',4,4'-tetrahydroxybenzophenone and
sodium 2,2'-dihycroxy-4,4'-methoxy-5'-sulfobenzophenone.
As the benzotriazole type ultraviolet absorber, there can be
mentioned, for example,
2-(2'-hydroxyphenyl)benzotriazole,
2-(2'-hydroxy-5'-methylphenyl)benzotriazole,
2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole,
2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole,
2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole,
2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole
2-(2'-hydroxy-3',5'-bis-
.alpha.,.alpha.-dimethylbenzylphenyl)-2H-benzotriazole,
2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole,
2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole.
As the salicylic acid derivative type ultraviolet absorber, there
can be mentioned, for example, phenyl salicylate, p-t-butylphenyl
salicylate and p-octylphenyl salicylate.
As the cyanoacrylate type ultraviolet absorber, there can be
mentioned, for example,
2-ethyl-2-cyano-3,3'-diphenyl acrylate and
2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate
As other ultraviolet absorbers, there can be mentioned, for
example,
dimethyl p-methoxybenzilidenemalonate,
dibenzoylresorcinole,
hexamethylphosphoric triamine,
tetraphenylsuccinylate dinitrile,
[2,2'-thiobis(4-t-octylphenolate)]-n-butylamine nickel (II)
nickel-bis(octylphenyl)sulfide,
nickel complex-3,5-di-t-butyl-4-hydroxybenzyl phosphoric acid
monoethylate,
nickel butyldithiocarbide,
naphthalene tetracarboxylic acid diimide,
bis-(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane,
2,2'-p-phenylene-bis(3,1-benzooxazin-4-one).
Among the compounds as described above, particularly preferred
are:
2-(2'-hydroxy-5'-methylphenyl)benzotriazole,
2-(2'-hydroxy5'-t-octylphenyl)benzotriazole,
2-[2'-hydroxy-3',5'-bis(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-benzotria
zole,
naphthalene tetracarboxylic acid diimide,
bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane and
2,2'-p-phenylene bis(3,1-benzooxazin-4-one).
While the ultraviolet absorber may be incorporated into a film by
adding during polymerization, adding before film-formation or by
previously forming a master batch, the method of forming the master
batch is preferred since the contaminations by the ultraviolet
absorber in the step can be reduced.
The content of the ultraviolet absorber in the shrinkable film is
preferably from 0.1 to 20% by weight and, more preferably from 0.2
to 10% by weight. If the content is less than 0.1% by weight, the
ultraviolet absorbing capacity is insufficient, whereas if it
exceeds 20 wt %, sublimation products are formed and bleedout of
the ultraviolet absorber to the film surface are caused and they
are no more usable.
The film according to the present invention has a shrinkage of from
20 to 80%, preferably, from 30 to 80% in one of longitudinal and
transverse directions (hereinafter referred to as the main
shrinking direction), after treatment for 5 minutes in an air oven
at 100.degree. C. In the shrinkable film according to the present
invention, the shrinkage in the main shrinking direction of less
than 20% is not preferred since the amount of shrinkage when shrunk
as a label is insufficient and the film is not closely fit to the
container.
Further, the shrinkable film according to the present invention has
a shrinkage from -10 to 15%, preferably from -5 to 10% and, more
preferably from -5 to 5% in the other direction perpendicular to
the main shrinking direction after treatment for 5 minutes in an
air oven at 100.degree. C.
A film having the shrinkage of larger than 15% is not preferred
since the film when shrunk as a label remarkably shrinks along the
longitudinal direction of the container to cause distortion of
patterns, etc.
For improving the durability of the shrinkable film, the strength
at break in the main shrinking direction is, preferably, from 20 to
40 kg/mm.sup.2, more preferably, from 25 to 40 kg/mm.sup.2.
The intrinsic viscosity [.eta.] of the shrinkable film according to
the present invention is, preferably, from 0.50 to 1.20, more
preferably, from 0.60 to 1.20 and, particularly preferably, from
0.65 to 1.20. If the intrinsic viscosity of the film is less than
0.50, crystallinity becomes higher, failing to obtain sufficient
shrinkage.
The heat of fusion of the shrinkable film according to the present
invention is preferably of not greater than 8 cal/g, more
preferably, not greater than 6 cal/g and, particularly preferably,
from 2 to 6 cal/g. A film with the heat of fusion of excess of 8
cal/g is not preferred since the shrinking characteristic is
reduced. It is considered that the reduction is due to the progress
of crystallization when the film is heated in a shrink tunnel to
cause an uneven shrinkage.
Further, the maximum shrinkage (neck-in ratio) of the shrinkable
film according to the present invention in the direction in
perpendicular to the main shrinking direction after treatment for 5
sec in water at 75.degree. C. while fixing both ends of the film in
the main shrinking direction is, preferably, from 1 to 20% and,
more preferably, from 2 to 15%. A film having the neck-in ratio in
excess of 20% is not preferred since distortion or oblique buckling
are caused frequently upon shrinking as a label.
The double refraction index of the shrinkable film according to the
present invention is, preferably, from 0.040 to 0.120 and, more
preferably, from 0.040 to 0.090.
A film with a double refraction index of lower than 0.040 is not
preferred since it is poor in warm water proofness, solvent
resistance, etc as a label. Further, a film with a double
refractive index in excess of 0.120 is not preferred since the
shrinking stress occurring along the main shrinking direction is
increased to reduce the shrinking characteristic.
In the shrinkable film according to the present invention, it is
also possible to provide a cushioning effect and improve breaking
strength of bottle after the packaging of glass bottles, etc. by
printing a foaming ink layer or laminating a thermoplastic resin
film or sheet having fine cells inside thereof on one or both
surfaces of the film. As the thermoplastic resin, any of known
thermoplastic resins such as polyvinyl chloride, polyethylene,
polypropylene, acrylic polymer, polystyrene and polyester resins
may be used.
There is no particular restriction for the thickness of the
shrinkable film according to the present invention but the
thickness, when used a shrinkable film for labelling use is,
preferably, from 10 to 300 .mu.m and, more preferably, from 20 to
200 .mu.m.
Description is to be made specifically for the method of producing
the film according to the present invention but the method is not
particularly limited to the following production methods.
After drying a polyester containing an appropriate amount of a
ultraviolet absorber and inorganic particles as the lubricant, etc.
as required by a usual drier such as a hopper drier or a paddle
drier or by using a vacuum drier, it was extruded at a temperature
of 200.degree. to 320.degree. C. As the extruding means, any of
known methods such as a T-die method or tubular method may be
employed. A non-stretched film obtained by rapid cooling after
extrusion is stretched in at least one of longitudinal and
transverse directions by, preferably, from 2.5 to 6.0 times and
more preferably, from 3.0 to 5.0 times. During the stretching step,
it is preferred that the film is uniformly heated in such a way
that the surface temperature T.sub.1 of the film is from Tg
-10.degree. C. to Tg+40.degree. C. (Tg means glass transition
temperature of the polyester) at the start of the stretching and is
stretched under such a condition that the surface temperature of
the film reaches to T.sub.1 -50.degree. C. to T.sub.1 +5.degree.
C., preferably, from T.sub.1 -50.degree. C. to T.sub.1 at the end
of the stretching. This stretching method is preferred to reduce
uneven thickness of the film and increase shrinkage at a lower
temperature.
For the stretching method, longitudinal mono-axial stretching by
means of rolls, transverse mono-axial stretching by means of tenter
and usual biaxial stretching are used. It is also possible to
stretch at a high ratio in one of the longitudinal and transverse
directions, while stretching at a ratio as low as possible in the
other direction. As the biaxial stretching method, known sequential
biaxial stretching or simultaneous stretching may be used. Further,
re-stretching may also be applied.
It is preferred for such stretched film to apply heat treatment at
60.degree. to 100.degree. C. for 0.1 sec to 5 min, more preferably,
from 0.1 sec to 60 sec in order to obtain a desired neck-in ratio.
The heat treatment can be conducted under fixing with stress,
relaxation of not more than 20% or tentering, for which known
method can be used such as contact with heating rolls, gripping by
a clip in a tenter, etc. Re-stretching may also be applied after
heat treatment.
It is also possible to apply corona discharging treatment on one or
both of the film surfaces during, before or after the stretching to
improve the adhesion of the film to the printing layer, etc.
Further, it is also possible to improve the ultraviolet absorbing
property, adhesion, antistatic property, slipperiness, light
screening property, etc. of the film by applying coating to one or
both of the film surfaces during, before or after the
stretching.
The thus obtained film is taken up into a product.
Shrinkable films used for labels of extremely excellent durability
upon transportation of containers and long-time storability of
contents in containers can be obtained by satisfying the above
requirements of the present invention.
The present invention is to be described more specifically
referring to examples, but the invention is not restricted only to
these examples unless it goes beyond the scope of the
invention.
The method of evaluating the film is shown below.
(1) Shrinkage factor
A film specimen in a strip form of 1 cm width was subjected to heat
shrinking treatment for 5 min in a geared oven at a temperature of
100.+-.2.degree. C. without load and the shrinkage was determined
in accordance with the following equation: ##EQU1## L.sub.o :
original length (10 cm) L: length after shrinking (cm)
(2) Light Transmittance
Transmittance at a wavelength of 390 nm was measured by using a
self-recording photospectrometer Model 340 manufactured by Hitachi
Limited.
(3) Intrinsic Viscosity of Film [.eta.]
200 mg of specimen was dissolved in 20 ml of a mixed solvent
comprising phenol/tetrachloroethane at 50/50 ratio by heating at
about 110.degree. C. for 1 hour, and the viscosity was measured at
30.degree. C.
(4) 10% Weight Loss Temperature (T.sub.10) of Ultraviolet
Absorber
Thermogravimetric analysis was conducted at a temperature
increasing rate of 10.degree. C./min by using SSC 580/TG-DTA 20
manufactured by Seiko Denshi Kogyo Co. and the temperature at which
the weight loss reached 10% was measured.
(5) Strength at Break (main shrinking direction)
A film of 15 mm width and inter-chuck length of 50 mm was stretched
at 20.degree. C., 65% RH by 50 mm/min using a TENSILON (UTN-III)
manufactured by TOYO-BALDWIN CO., and the strength of the film upon
break was divided by the initial cross sectional area, which was
expressed by kg/mm.sup.2.
(6) Film Durability
After making a film into a cylindrical label, it was fitted over a
PET bottle and caused to shrink by passing through a shrink
tunnel.
The upper surface of the label was rubbed with a pencil of H
hardness and evaluation was made as X for those easily broken and
as O for those showing no substantial change.
(7) Storability of Contents
In the same procedures as in (6) above, SAKE was filled in a
transparent PET bottle and the film was shrunk. In this case, the
film was shrunk so as to cover more than 95% of the side of the
bottle.
After capping the PET bottle and left for three days outdoor,
change of the SAKE contents was observed. Evaluation was made as X
for those causing yellow discoloration and deterioration in the
quality and as O for those showing no changes in view of the
appearance.
EXAMPLE 1
Polyethylene terephthalate with [.eta.]=0.66 was blended with 20%
by weight of a ultraviolet absorber:
2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole (Cyasorb UV5411;
registered trade mark of products from Cyanamid Co.)(T.sub.10
=232.degree. C.), and then kneaded by using a two shaft extruder of
30 mm.phi., to obtain a master batch polyester (A).
Further, a copolyester (B) with [.eta.]=0.70 comprising 80 mol % of
terephthalic acid unit and 20 mol % of isophthalic acid unit as the
acid component, 97 mol % of ethylene glycol unit and 3 mol % of
diethylene glycol unit as the glycol component and containing 400
ppm of amorphous silica of 1.2 .mu.m of average particle size was
prepared. The master batch polyester (A) and the copolyester (B)
were blended at 30/70 weight % ratio.
After drying the blend as described above by means of a usual
method, it was extruded at 280.degree. C. from an extruder and
rapidly cooled and solidified to obtain a non-stretched film. The
resultant not-stretched film was introduced into a tenter in which
it was stretched transversely by 4.0 times at a stretching
temperature of 80.degree. C. and applied with heat treatment at
85.degree. C. for 8 sec, cooled and then taken up. During the heat
treatment, 2% relaxation was applied in the longitudinal direction.
The average thickness of the resultant film was about 40 .mu.m.
EXAMPLE 2
A master batch polyester (C) was obtained by using
2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Tinuvin P;trade mark
of products manufactured by Ciba-Geigy, Ltd.) (T.sub.10
=198.degree. C.) as the ultraviolet absorber to be kneaded in the
polyester (A) of Example 1.
The resultant polyester (C) and the polyester (B) were blended at
20/80 weight % ratio, extruded and made into a film in the same
manner as in Example 1 to obtain a film of about 40 .mu.m of
average thickness.
COMPARATIVE EXAMPLE 1
Using the polyester (B), a film of about 40 .mu.m average thickness
was obtained by applying extrusion and film-formation in the same
way as in Example 1.
COMPARATIVE EXAMPLE 2
A polyvinyl chloride shrinkable film (average thickness of 40
.mu.m) containing 2.0% by weight of the same ultraviolet absorber,
2-(2'-hydroxy-5'-methylphenyl)benzotriazole as in Example 2 was
used as the Comparative Example 2.
EXAMPLE 3
After drying a copolyester (D) with [.eta.]=0.72 comprising a
terephthalic acid unit as the acid component and 88 mol % of
ethylene glycol unit and 12 mol % of neopentyl glycol unit as the
glycol component, 20 wt % by weight of 2-[2'-hydroxy-3',
5'-bis(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-benzotriazole
(Tinuvin 234, registered trade mark of products manufactured by
Ciba-Geigy, Ltd.) (T.sub.10 =305.degree. C.) was kneaded therewith
to obtain a master batch polyester (E).
The polyester (D) and the polyester (E) was blended at 80/20 weight
% ratio, extruded at 280.degree. C. and rapidly cooled and
solidified to obtain a non-stretched film. The resultant
non-stretched film was stretched by 3.5 times at 85.degree. C. in
the longitudinal direction by the difference in the circumferential
speeds between a heating roll and a cooling roll and, heat
treatment was applied to the film by contacting the film with a
heating roll at 92.degree. C. for 0.2 sec. The average thickness of
the resultant film was 50 .mu.m.
EXAMPLE 4
A copolyester (F) with [.eta.]=0.79 comprising terephthalic acid
unit as the acid component and 80 mol % of ethylene glycol unit and
20 mol % of 1,4-cyclohexane dimethanol unit as the glycol component
was blended with the polyester (E) at 80/20 weight % ratio. The
blend was extruded and formed into a film in the same manner as in
Example 3 to obtain a film of 50 .mu.m of average thickness.
The properties of the resultant films are collectively shown in
Table 1.
TABLE 1
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Shrinkage Light (%) transmittance at Strength at longitudinal
transverse 390 nm Break Film Storability of direction direction (%)
(kg/mm.sup.2) Durability contens
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Example 1 3 48 4.5 31.2 O O 2 2 51 4.8 30.7 O O 3 52 0 3.7 28.7 O O
4 54 -1 3.7 27.6 O O Comparative 2 54 76.0 30.3 O X Example 1
Comparative 6 57 4.8 13.0 X O Example 2
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